The present invention relates to printing devices and, more particularly, to a printer system adapted for printing on labels coated with a pressure-sensitive adhesive and carried by a web of release material.
Label printing and dispensing devices are known in which variable information is printed on each of a series of labels having a pressure-sensitive adhesive coating the back surface thereof, with printing being accomplished while the labels are mounted on a strip or web of a release material. Such printers are suitable for use in an automatic computing scale system which weighs food products or other articles. The printer in such a system prints various information, such as the weight, the price per unit weight, and computed value of an article on a label which is thereafter affixed to the article. Computing scale systems of this type have found wide use in food markets which sell commodities, such as meat, in prepackaged form with a printed label being attached to each package prior to arrangement in the display case.
Typically in such printers, the strip of release material carrying the printed labels is caused to pass around a sharp edge which strips the labels from the release material. The labels are thereafter transferred to a label application station where they are applied to the weighed articles. Some types of systems, such as shown in U.S. Pat. No. 3,342,661, issued Sept. 19, 1967, to Arvidson et al, provide for automated application of the labels to the articles. Other systems, such as shown in U.S. Pat. No. 3,556,898, issued Jan. 19, 1971, to Allen, and U.S. Pat. No. 3,985,603, issued Oct. 12, 1976, to Berner, simply deliver the printed label to a chute where the label is held with its adhesive-coated side facing upward for manual application of the label to the articles.
Generally, a printer of this type includes a supply roll from which the web of release material bearing the unprinted labels is unreeled. The web is transported past one or more printing stations and, thereafter, passes around the sharp edge which removes the printed labels from the release material. The web is then wound onto a take up roll or otherwise disposed of. Commonly, the supply roll may be mounted for free rotation on a support shaft while the web of release material is unreeled from the supply roll by means of a web drive mechanism which positively engages the web. Such an arrangement is shown in U.S. Pat. No. 3,526,189, issued Sept. 1, 1970, to Allen, and U.S. Pat. No. 3,556,898, issued Jan. 19, 1971, to Allen.
Where a take up roll is provided for collecting the web of release material after removal of the labels, this take up roll may be driven by a separate drive mechanism, as shown in U.S. Pat. No. 4,111,121, issued Sept. 5, 1978, and U.S. Pat. No. 3,729,362, issued Apr. 24, 1973, to French et al. Alternatively, the take up roll may be driven by a belt drive arrangement connected to the drive mechanism for the web drive rollers, as shown in U.S. Pat. No. 3,696,967, issued Oct. 10, 1972, to Moore et al and U.S. Pat. No. 4,120,245, issued Oct. 17, 1978, to Karp et al. Typically, such a belt drive arrangement includes a slip clutch connection between the web drive and the take up roll so that the take up roll may rotate more slowly as the roll radius increases. Since the supply roll in such systems is not positively driven but rather rotates as the web is unreeled by the web drive mechanism, a brake mechanism, as shown in the above identified French et al '362 patent, may be connected to the supply roll to prevent it from continuing to rotate after a length of the web has been withdrawn from the supply roll.
Prior art web drive mechanisms, including arrangements for rotating a take up roll and also for limiting the rotation of a supply roll, are relatively complicated. Additionally, web drive mechanisms of the type which include separate drive motors for the web and the take up roll are relatively expensive. The belt drive arrangements of some systems which extend between the various rotating elements of the printer are also subject to wear and to failure. Accordingly, it is seen that there is a need for a simple, reliable supply mechanism for transporting past a printer a web of release material, bearing labels which are to be printed, and for winding the web of release material onto a take up roll after removal of the labels.
Another problem encountered with prior art printers results from the inertia of the supply roll and the take up roll. Typically, the web of relese material is moved past the printer in an incremental manner. That is, the web is moved by a distance equal to the spacing between the centers of adjacent labels between each printing operation, while being held stationary during printing. It will be appreciated that if a relatively large supply roll is utilized in order to minimize the frequency with which new supply rolls must be loaded into the printer, such a supply roll will present substantial resistance to rotation by reason of its inertia. As a consequence, it has been necessary to provide high torque drive mechanisms for both the supply roll and the take up roll to overcome the inertia of these rolls where rapid incremental rotation of the rolls is required. As a consequence, the costs of the overall printer systems have been increased substantially.
Accordingly, it is seen that there is a need for a web supply arrangement for transporting a web past a printer, while minimizing the torque requirements of the drive mechanism.